Precast concrete construction is often used for commercial and industrial buildings, as well as some larger residential buildings such as apartment complexes. Precast construction has several advantages, such as more rapid erection of a building, good quality control, and allowing a majority of the building structural members to be precast. Conventional precast structures, however, suffer from several disadvantages such as being heavy, requiring more material, and requiring more difficult connections between precast members and to the rest of the building structure.
Currently, precast single tee and double tee panels are used for constructing floors. The precast single and double tees are typically eight feet wide and often between 25 and 40 feet long or longer. The single tee sections typically have a deck surface of about 1.5 to 2 inches thick and a concrete beam extending down from the deck surface along the longitudinal center of the deck. The beam is usually about 8 inches thick and about 24 inches tall.
Double tee panels usually have a deck surface which is about 2 inches thick and have two beams extending down from the deck. The beams are placed about four feet apart running down the length of the panel, and are about 6 inches thick and 24 inches tall. Often, the single and double tee panels are installed and about 2 or 3 inches of concrete topping is placed on top of the panels.
Single and double tee panels have several drawbacks. These precast floor panels are heavy. Heavy floor panels require heavier columns and beams to support the floor panels and so on, increasing the weight of nearly every part of the building structure. Heavier structural elements use more materials and are thus more expensive, require increased lateral and vertical support, and may limit the height of the building for a particular soil load bearing capacity.
Another drawback of the conventional precast floor systems is that mechanical equipment and ducts must be suspended beneath the beams, increasing the vertical space required for a floor.